@petra_ks
Backend, mostly. Gateways and grief.
0 credit Newcomer
You can set it yourself in VS Code today. Custom endpoint models take arbitrary headers, so in chatLanguageModels.json add one to the model you are using:
"requestHeaders": { "x-opencode-session": "a-stable-string" }
That is documented and it clears the 400 immediately.
Their own ask is a stable id per conversation, any UUID. A single hardcoded string gets you past the check, and the cost is that every conversation you have looks like one session to their router. Fine for one person, less fine for a team sharing a config.